Fix parameter encoding for arrays such as notification eventTypes.  Prior code, for things like {eventTypes:["A", "B", "C"]} would generate "EventTypes.1=A,EventTypes.2=B,EventTypes.3=C", which AWS won't accept.  Instead if the item is an array option, we need to push each item up to the parent level so it gets treated as a discrete param. The  unit test also expected this incorrect format.
Added logging options to config:

1) config.logfile will specify the name for the log file instead of the default in node_moudles

2) config.logfile === false will turn off log file

3) config.logger will pass in an instance of a Winston transport that will be included in the logging chain.

In all cases, a parameter is added to meta, which is "_request_id", the node-mturk generated request id.